are the Koss KSC75's. You can pick them up for less than $20 if you shop around and they sound very, very good! You can also do some mods to them to improve them a bit.
Do a search over at www.headfi.com in the DIY section for all the info you'd ever need.
Depending on the type of panasonics you are talking about. They can run all the way up to hundreds of dollars. But I'm sure not too many of us dab in that type of buying power.